Hydrogenation cyclohexene and

The major products of the radiolysis of liquid cyclohexane are hydrogen, cyclohexene and bicyclohexyl with G-values of 5.55, 3.27 and 1.95 respectively . The reactions involved are given in the general mechanism outlined by Dyne , viz. 

The yields of hydrogen, cyclohexene, and bicyclohexyl decrease markedly on adding C02 or SF6 to cyclohexane (56, 57), and these decreases can be qualitatively accounted for in this way. The energy taken up by XY in Reaction 7 may result in formation of products derived from the solute. 

Table I. Radiolytic Yields of Hydrogen, Cyclohexene, and Bicyclohexyl from Cyclohexane...

Pure Cyclohexane. The major products from the radiolysis of cyclohexane are hydrogen, cyclohexene, and bicyclohexyl. Dewhurst (4) proposed that these could be formed by the production of hydrogen atoms and cyclohexyl radicals, followed by abstraction by hydrogen atoms and recombination and disproportionation of the cyclohexyl radicals. Dyne and Jenkinson (5) showed that part of the hydrogen yield is unimolecu-larly formed. It was suggested that excited cyclohexane molecules give... 

Cyclohexane and Nitrous Oxide. The effect of nitrous oxide on the yields of hydrogen, cyclohexene, and bicyclohexyl at conventional dose rates has been studied by Sagert and Blair (12), and their results are included in Figures 7 and 8. These authors explain their results by the replacement of Reaction lb, (C6Hi2+ + e C6Hi2 ), by Reactions 10 to 12. 

Figure 7. Hydrogen, cyclohexene, and bicyclohexyl yields from molar solutions of sulfur hexafluoride in cyclohexane...

Cyclohexane and SF . Sulfur hexafluoride reacts rapidly with electrons, and its effect on the hydrogen, cyclohexene, and bicyclohexyl yields has been explained (12) by the replacement of Reaction lb by Reactions 14 and 15. 

The yields of hydrogen, cyclohexene and bicyclohexyl have been taken from Reference 39, those of the other products from References 18 and 40. 

Hydrogen, cyclohexene, and bicyclohexyl are the major products from radiolyses of cyclohexane. Scission of a CH bond is a major reaction mode. At high doses, polymeric species are formed upon secondary reaction of cyclohexyl radicals with cyclohexene molecules. 

Wilkinson Hyd.rogena.tion, One of the best understood catalytic cycles is that for olefin hydrogenation in the presence of phosphine complexes of rhodium, the Wilkinson hydrogenation (14,15). The reactions of a number of olefins, eg, cyclohexene and styrene, are rapid, taking place even at room temperature and atmospheric pressure but the reaction of ethylene is extremely slow. Complexes of a number of transition metals in addition to rhodium are active for the reaction. 

Allylic conjugation stabilizes carbanions, and pAT values of 43 (in cyclohexylamine) and 47—48 (in THF-HMPA) have been determined for propene. On the basis of exchange rates with cesium cyclohexylamide, cyclohexene and cycloheptene have been found to have pAT values of about 45 in cyclohexylamine. The hydrogens on the sjp-... 

A polymeric form of the reagent from hydrogen fluoride and poly(4-vinylpyndine) is especially easy to handle [I0 Other tertiary amines can also be employed [II], and a two-phase mixture of hydrogen fluoride-melamine-pentane hydrofluorinates cyclohexene to fluorocyclohexane m 98% yield [12]... 

If the hydroxy-acid is heated with hydrobromic acid, it is converted into l-methyl-l-bromocyclohexane-4-carboxylic acid, and this is decomposed by boiling with sodium carbonate with loss of hydrogen bromide and with formation of 1-methyl-A cyclohexene-4-carboxyhc acid—... 

The rate of transfer hydrogenation also varies markedly with donor structure. For cyclohexene, 1 -methylcyclohexene, l-methyl-4-isopropyl-cyclohexene,and l-methyl-4-f-butyIcycIohexene as donor in the above hydrogenations, after 1 min the reduction was 11, 78, 99, and 99% complete, respectively (97). 

The preparation of Pans-1,2-cyclohexanediol by oxidation of cyclohexene with peroxyformic acid and subsequent hydrolysis of the diol monoformate has been described, and other methods for the preparation of both cis- and trans-l,2-cyclohexanediols were cited. Subsequently the trans diol has been prepared by oxidation of cyclohexene with various peroxy acids, with hydrogen peroxide and selenium dioxide, and with iodine and silver acetate by the Prevost reaction. Alternative methods for preparing the trans isomer are hydroboration of various enol derivatives of cyclohexanone and reduction of Pans-2-cyclohexen-l-ol epoxide with lithium aluminum hydride. cis-1,2-Cyclohexanediol has been prepared by cis hydroxylation of cyclohexene with various reagents or catalysts derived from osmium tetroxide, by solvolysis of Pans-2-halocyclohexanol esters in a manner similar to the Woodward-Prevost reaction, by reduction of cis-2-cyclohexen-l-ol epoxide with lithium aluminum hydride, and by oxymercuration of 2-cyclohexen-l-ol with mercury(II) trifluoro-acetate in the presence of ehloral and subsequent reduction. ... 

The stereochemistry of addition of hydrogen halides to alkenes depends on the structure of the alkene and also on the reaction conditions. Addition of hydrogen bromide to cyclohexene and to E- and Z-2-butene is anti.6 The addition of hydrogen chloride to 1 -methylcyclopentene is entirely anti when carried out at 25° C in nitromethane.7... 

Usually the benzyl ether is dissolved in EtOH and cyclohexene, and 20% Pd(OH)2/C is added (1 10 catalyst-substrate by weight) and stirred under reflux for the required period (thin layer chromotography monitoring).246 Without cyclohexene, the benzyl ether was usually recovered, signifying that the EtOH solvent is not a good hydrogen donor under these conditions. 

Catalytic hydrogenation of azo compounds over Pt or Ra-Ni often leads to hydrogenolysis. 551 Catalytic transfer hydrogenolysis using cyclohexene and Pd is also used for the conversion of azobenzenes to anilines.552... 

We have shown that a number of aliphatic ethers, containing steric-ally accessible p-hydrogen atoms, are cleaved in good yield when the tetrahalogenoanthranilic acids are diazotised in ethers 128,59). Diethyl ether is cleaved to the tetrahalogenophenetole (90) and methyl-cyclohexyl ether affords the tetrahalogenoanisole. In this latter reaction we were able to detect cyclohexene and therefore a plausible, but as yet unproved, mechanism is as shown. 

Unlike cyclohexene, its oxa analog, 3,4-dihydro-2//-pyran, undergoes facile reduction to tetrahydropyran in yields ranging from 70 to 92% when treated with a slight excess of triethylsilane and an excess of either trifluoroacetic acid or a combination of hydrogen chloride and aluminum chloride (Eq. 69).146 This difference in behavior can be understood in terms of the accessibility of the resonance-stabilized oxonium ion intermediate formed upon protonation. 

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